> SLOTD-CLASSES-EQ is called from %UPDATE-SLOTS, particularly this piece of code:
>
> ((and (equal nlayout olayout)
> (equal (mapcar #'car owrapper-class-slots)
> (mapcar #'car nwrapper-class-slots))
> (slotd-classes-eq (slot-value class 'slots) eslotds))
> owrapper)
>
> So it looks like that SB-MOP did not expect that number of slots might
> be different at this point.
I've looked some more into this, the problem is that this code assumes
that there are only instance-allocated slots and class-allocated,
while we have database-allocated ones.

This problem (regression) when using Elephant was already reported by
Kevin Raison.
I don't know what's the current status, but I can add some details
which hopefully will help to fix this.
So this problem happens in SLOTD-CLASSES-EQ. The reason is that number
of slots is different,
oslotds = (#<ELEPHANT::TRANSIENT-EFFECTIVE-SLOT-DEFINITION ELEPHANT::OID>
#<ELEPHANT::TRANSIENT-EFFECTIVE-SLOT-DEFINITION ELEPHANT::SPEC>
#<ELEPHANT::INDEXED-EFFECTIVE-SLOT-DEFINITION NAME>
#<ELEPHANT::ASSOCIATION-EFFECTIVE-SLOT-DEFINITION JOBS>)
nslotds = (#<ELEPHANT::TRANSIENT-EFFECTIVE-SLOT-DEFINITION ELEPHANT::OID>
#<ELEPHANT::TRANSIENT-EFFECTIVE-SLOT-DEFINITION ELEPHANT::SPEC>
#<ELEPHANT::INDEXED-EFFECTIVE-SLOT-DEFINITION NAME>)
I.e. JOBS slot was dropped.
SLOTD-CLASSES-EQ is called from %UPDATE-SLOTS, particularly this piece of code:
((and (equal nlayout olayout)
(equal (mapcar #'car owrapper-class-slots)
(mapcar #'car nwrapper-class-slots))
(slotd-classes-eq (slot-value class 'slots) eslotds))
owrapper)
So it looks like that SB-MOP did not expect that number of slots might
be different at this point.
I don't understand SBCL CLOS implementation, so take it with a grain
of salt, but it seems like SBCL might be confused because JOBS (and
NAME) is a "virtual" slot which is not allocated in instance. Neither
is NAME.
So it compares nlayout and olayout which contain only instance slots
OID and SPEC:
NEW:((ELEPHANT::OID . T) (ELEPHANT::SPEC OR LIST STRING))
OLD:((ELEPHANT::OID . T) (ELEPHANT::SPEC OR LIST STRING))
And thinks that rest is same too.
HTH